1. Field of the Invention
The present invention relates to an image display device, specifically an image display device which produces an image by joining a plurality of divided frames to generate a single frame. The present invention also relates to an image control device and method for correcting an image displayed on the image display device.
2. Description of the Related Art
Cathode ray tubes (CRTs) are widely used in image display devices such as television receivers or computer monitors. Inside a cathode ray tube (hereinafter also simply referred to as xe2x80x9cinside the tubexe2x80x9d), provided are an electron gun and a fluorescent screen. The electron gun produces an electron beam emitted toward the fluorescent screen. The electron beam scans to form a scanned image.
A cathode ray tube generally has a single electron gun. In recent years, however, a multiple-gun cathode ray tube, comprising two or more electron guns, has been developed. A multiple-gun cathode ray tube produces an image as follows. Each of the electron guns produces its own electron beam, and a plurality of divided frames are generated. The divided frames are joined to form a single frame. The related art concerning multiple-gun cathode ray tubes is disclosed in, for example, Publication of Examined Japanese Utility Model Application No. Sho 39-25641, Publication of Examined Japanese Patent Application No. Sho 42-4928 and Publication of Unexamined Japanese Patent Application No. Sho 50-17167. A multiple-gun cathode ray tube has several advantages of a smaller depth dimension and a larger screen, as compared to a single-gun cathode ray tube.
When joining a plurality of divided frames to generate a single frame in a multiple-gun cathode ray tube, it is desirable that the joint area of the divided frames is as inconspicuous as possible. The related art is, however, insufficient for making the joint area of the divided frames inconspicuous. Thus, there is a problem that high picture quality cannot always achieved throughout the entire screen of a multiple-gun cathode ray tube.
A cathode ray tube for displaying color images produces electron beams for a set of primary colors for color display. The electron beams for their respective colors are influenced by different magnetic fields from color to color and may fail to converge. However, in order to reproduce input signals accurately on the screen, the electron beams for respective colors have to converge on the screen. Such a phenomenon in which the positions where the electron beams strike the screen are deviated from each other is called misconvergence.
Since a screen of a cathode ray tube is generally rectangular, the distance traveled by the electron beam reaching the screen is the longest at each four corner of the screen. An image displayed on a screen of a cathode ray tube, therefore, usually appears distorted in a form of pincushion. Such distortion of an image is called xe2x80x9cimage distortionxe2x80x9d.
The related art practice followed in minimizing image distortion is to optimize a deflection magnetic field generated by a deflection yoke. In recent years, however, image display devices have greater aspect ratios and flatter screens. This makes it impossible to correct image distortion completely only by a deflection magnetic field generated by a deflection yoke. There are several methods to correct image distortion which remains uncorrected by a deflection yoke. One example is to modulate a deflection current fed to a deflection yoke. But this method of modulating a deflection current requires an additional circuit for modulation, which causes a problem of cost increase.
Correction for misconvergence is made in a manner basically similar to the case of image distortion. That is, the electron beams for their respective colors are designed to converge throughout the entire screen by means of distribution of deflection magnetic fields generated by a deflection yoke itself. As in the case of image distortion, however, it is difficult to correct misconvergence completely only by distribution of magnetic fields.
The related art practice followed in correcting misconvergence which remains uncorrected by a deflection yoke is to move the electron beams for their respective colors separately by using an additional correction subyoke separate from a deflection yoke, thereby converging the electron beams accurately. This method requires not only a subyoke but an additional circuit for driving the subyoke, resulting in an increase in cost of manufacturing.
As described above, the related art adopts the method of correcting image distortion or misconvergence by using deflection magnetic fields. Adjustments for correction by using deflection magnetic fields involve spreading an image repeatedly to the entire screen in each of the horizontal direction and the vertical direction. This method therefore has some other undesirable aspects such as low worker efficiency and variations according to worker, which makes it difficult to effect optimal adjustment of image distortion constantly.
Moreover, eliminating image distortion or misconvergence by using a deflection yoke also involves distorting deflection magnetic fields forcedly, which results in non-uniform magnetic fields. The distorted magnetic fields cause deterioration in focusing characteristics such as spotsize of an electron beam, resulting in deterioration in resolution.
The description given above has been made concerning the problems common to cathode ray tubes, such as image distortion, misconvergence and correction therefor. In the case of multiple-gun cathode ray tubes, these problems further influence precision in joining a plurality of divided frames. It is therefore desirable that, in the case of multiple-gun cathode ray tubes, image distortion or misconvergence is properly corrected and a plurality of divided frames are joined accurately so that the joint areas of the divided frames are inconspicuous.
Furthermore, cathode ray tubes are under influences of terrestrial magnetism or others. The influences of terrestrial magnetism or others vary according to the area of use and also cause image distortion. Image distortion due to terrestrial magnetism also exerts an undesirable influence on the display of the joint areas of the divided frames in the case of multiple-gun cathode ray tubes. Multiple-gun cathode ray tubes of the related art, however, are insufficient for display control of the joint areas in consideration of the area of use.
Lastly, image display performance of a cathode ray tube also deteriorates due to change of processing circuits such as a deflection circuit with time. Multiple-gun cathode ray tubes of the related art are also insufficient for display control of the joint areas in consideration of change with time.
The present invention has been made to overcome the foregoing problems. An object of the present invention is to provide an image control device and method, and image display device, capable of producing an image of high quality and joining a plurality of divided frames with the joint areas being inconspicuous in view of both position and luminance.
An image control device according to a first aspect of the present invention is provided for correcting an image produced on an image display device which produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image control device comprises: first converting means for converting a picture signal inputted unidimensionally to the image display device to discrete two-dimensional image data; first operating means for performing an operation for correcting horizontally an array of pixels in the two-dimensional image data, so that the divided frames are joined properly in position in the horizontal direction and displayed when the image display device produces an image; and means for storing image data for storing, in the order of write address, the image data outputted from the first operating means, the means for storing image data capable of reading the stored image data in the same order as the order of write address or in the order different from the order of write address. The image control device further comprises: means for generating an address for generating a write address for image data with respect to the means for storing image data, the means for generating an address capable of generating a read address for the image data stored in the means for storing image data in the same order as the order of write address or in the order different from the order or write address; second operating means for performing an operation for correcting, vertically with respect to the original state of the image data, an array of pixels in the image data outputted from the means for storing image data, so that the divided frames are joined properly in position in the vertical direction and displayed when the image display device produces an image; and second converting means for converting the image data corrected in the second operating means to a picture signal for display on the image display device and outputting the picture signal.
An image control device according to a second aspect of the present invention is provided for correcting an image produced on an image display device which produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image control device comprises: means for position control for performing control in such a manner that a unidimensional picture signal inputted to the image display device is converted to discrete two-dimensional image data, and performing control in such a manner that an array of pixels in the image data is corrected so that the divided frames are joined properly in position and displayed when the image display device produces an image; means for luminance control for performing control in such a manner that, after the position correction is made in the means for position control, the image data is corrected in luminance, independently of the position correction, so that the divided frames are joined properly in luminance and displayed; and converting means for converting the image data corrected in luminance in the means for luminance control to a picture signal for display on the image display device and outputting the picture signal.
An image control method according to the first aspect of the present invention is provided for correcting an image produced on an image display device which produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image control method involves: converting a unidimensional picture signal inputted to the image display device into discrete two-dimensional image data; performing an operation for correcting horizontally an array of pixels in the two-dimensional image data, so that the divided frames are joined properly in position in the horizontal direction and displayed when the image display device produces an image; and storing, in the order of write address, the horizontally corrected image data on means for storing image data. The image control method further involves; reading the stored image data in the same order as the order of write address or in the order different from the order of write address; performing an operation for correcting, vertically with respect to the original state of the image data, an array of pixels in the image data outputted from the means for storing image data, so that the divided frames are joined properly in position in the vertical direction and displayed when the image display device produces an image; and converting the vertically corrected image data to a picture signal for display on the image display device and outputting the picture signal.
An image control method according to the second aspect of the present invention is provided for correcting an image produced on an image display device which produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image control method involves: performing control in such a manner that a unidimensional picture signal inputted to the image display device is converted to discrete two-dimensional image data, and performing control in such a manner that an array of pixels in the image data is corrected in position so that the divided frames are joined properly in position and displayed when the image display device produces an image; performing control in such a manner that, after the position correction is made, the image data is corrected in luminance, independently of the position correction, so that the divided frames are joined properly in luminance and displayed; and converting the image data corrected in luminance to a picture signal for display on the image display device and outputting the picture signal.
An image display device according to the first aspect of the present invention produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image display device comprises: first converting means for converting a unidimensional picture signal inputted to the image display device to discrete two-dimensional image data; first operating means for performing an operation for correcting horizontally an array of pixels in the two-dimensional image data, so that the divided frames are joined properly in position in the horizontal direction and displayed when the image display device produces an image; and means for storing image data for storing, in the order of write address, the image data outputted from the first operating means, the means for storing image data capable of reading the stored image data in the same order as the order of write address or in the order different from the order of write address. The image display device further comprises: means for generating an address for generating a write address for image data with respect to the means for storing image data, the means for generating an address capable of generating a read address for the image data stored in the means for storing image data in the same order as the order of write address or in the order different from the order or write address; second operating means for performing an operation for correcting, vertically with respect to the original state of the image data, an array of pixels in the image data outputted from the means for storing image data, so that the divided frames are joined properly in position in the vertical direction and displayed when the image display device produces an image; second converting means for converting the image data corrected in the second operating means to a picture signal for display on the image display device and outputting the picture signal; and image display means for displaying an image based on the picture signal for display outputted from the second converting means.
An image display device according to the second aspect of the present invention produces an image based on a picture signal inputted unidimensionally, and joins a plurality of divided frames to generate a single frame. The image display device comprises: means for position control for performing control in such a manner that a unidimensional picture signal inputted to the image display device is converted to discrete two-dimensional image data, and performing control in such a manner that an array of pixels in the image data is corrected so that the divided frames are joined properly in position and displayed when the image display device produces an image; means for luminance control for performing control in such a manner that, after the position correction is made in the means for position control, the image data is corrected in luminance, independently of the position correction, so that the divided frames are joined properly in luminance and displayed; converting means for converting the image data corrected in luminance in the means for luminance control to a picture signal for display on the image display device and outputting the picture signal; and image display means for displaying an image based on the picture signal for display outputted from the converting means.
In the image control device and method, and in the image display device according to a first aspect of the present invention, performed is an operation for correcting horizontally an array of pixels in the two-dimensional image data, so that a plurality of divided frames are joined properly in position in the horizontal direction and displayed. The horizontally corrected image data is stored, in the order of write address, on the means for storing image data. The stored image data is read in the same order as the order of write address or in the order different from the order of write address. Then, performed is an operation for correcting, vertically with respect to the original state of the image data, an array of pixels in the image data outputted from the means for storing image data, so that the divided frames are joined properly in position in the vertical direction and displayed. In the image control device and method, and in the image display device according to the first aspect of the present invention, an operation for correcting image data is performed mainly based on correction data obtained from an image displayed on a screen, for correcting the status of display of the image. The first aspect of the present invention does not involve correcting image data based on electron beam detecting means.
In the image control device and method, and in the image display device according to the second aspect of the present invention, position control is effected over image data so that a plurality of divided frames are joined properly in position and displayed. After the position correction is made, the image data is corrected in luminance independently of the position correction, so that the divided frames are joined properly in luminance. A main application of the image control device and method, and the image display device according to the second aspect of the present invention is a cathode ray tube which comprises: a plurality of electron guns which emit a plurality of electron beams for scanning an available picture area and an over-scan area outside the available picture area; and electron beam detecting means which is provided in the over-scan area on the side of the joint area of the adjacent divided frames and outputs light or an electrical signal in response to the incident electron beam. In the second aspect of the present invention, the means for position control performs control for correcting the image data using second correction data obtained based on the light or the electrical signal outputted from the electron beam detecting means in addition to the first correction data obtained from an image displayed on a screen for correcting the status of display of the image.
Other and further objects, features and advantages of the invention will appear more fully from the following description.